Marvel Schebler Power System

How it works

With the throttle valve (6) in slow or just off slow idle position, fuel rises up through the nozzle (14) and out the nozzle air bleeds (15) to fill the accelerating well (16) to approxi­mately the height of the fuel level in the fuel bowl (1).

As the engine speed is increased from the slow idle position the air flow through the venturi (17) is gradually increased, and as the idle system begins to diminish the velocity through the venturi (17) is high enough to create a pres­sure at the tip of the nozzle (14) slightly less than the pressure in the fuel bowl chamber (9) and the accelerating well (16). Fuel, therefore, feeds from the fuel bowl (1) through the open­ing between the power (load) adjusting needle (18) and the power adjusting needle seat (19), through the power jet (20) and out the nozzle ( 14) to be discharged into the air stream at the venturi ( 17) . At the same time, the fuel that is stored in the accelerating well (16) is also forced through the nozzle air bleeds (15) into the nozzle (14). But, because the size of the power jet (20) and the position of the power ad­justing needle (18) restrict the amount of fuel which can enter the nozzle (14), the fuel in the ·accelerat­ing well (16) will soon be exhausted and air will then enter through the nozzle air bleeds (15) to mix with the fuel passing through the nozzle (14). The amount of air that can enter into the nozzle (14) is limited by the size of the nozzle air vent (21).

The result of air bleed­ing into the nozzle (14) is, to help atomize or break up the fuel into finer par­ticles, to regulate the quan­tity and the rate of dis-charge of the fuel fed from the accelerating well (16), during acceleration, and to provide the correct mixture proportions for full throttle operation.

As the throttle valve is opened toward the wide open position the velocity through the ven­turi (17) continues to increase, lowering the air pressure at the nozzle (14) and resulting in additional fuel being supplied to the engine as the speed is increased.

When the throttle valve (6) is opened sud­denly from slow or just off slow idle position, the fuel stored in the accelerating well (16) is forced out through the nozzle air bleeds (15) very rapidly and serves to provide the extra richness required by the engine to meet the sudden load. When the throttle valve (6) is closed fuel again fills the accelerating well (16), ready for the next acceleration.